Description of the Related Art
This invention relates to a dental cream packaged in a plastic laminate tube, mechanical dispenser, flexible sachet or the like. In particular, it relates to a dental cream in compatible contact with a polyolefin surface of a package such as a plastic laminate dental cream tube, mechanical dispenser or flexible sachet.
Dental creams have been packaged for many years in flexible metal tubes such as wax lined lead tubes, unlined aluminum tubes or aluminum tubes having an epoxy resin lacquer coating thereon. In recent years, flexible form-retaining laminated plastic tubes have been increasingly used.
Plastic laminated dental cream tubes typically comprise in inner polyolefin resin layer which is in direct contact with the dental cream and at least one intermediate layer, including an aluminum foil layer which inhibits loss of flavor from the dental cream. Desirably, an intermediate paper layer which provides stiffness to the tube is also present. The outer layers are typically of polyolefin resins, one of which may be colored white and bear printed indicia with a clear polyolefin laminate overlay to protect the indicia. Additional intermediate laminate layers of flexible plastic may also be present.
Mechanical dental cream dispensers may also have a polyolefin surface in contact with dental cream contained therein. In fact, the polyolefin itself may be the housing of the dispenser. Flexible sachet packets may also have a polyolefin surface in contact with dental cream.
Dental creams typically contain a liquid vehicle of water and humectant, a gelling agent solid vehicle and a water-insoluble dental polishing agent. A surface active is also generally included. Dental creams composed of such materials wherein the humectant comprises glycerine and sorbitol and the polishing material is an alkaline earth metal salt such as dicalcium phosphate have been successfully packaged in flexible metal toothpaste containers including aluminum tubes which are unlined or which have an internal coating of an epoxy resin lacquer layer. However, it is observed that when such dental creams are differently packaged in containers having an interior polyolefin surface such as plastic laminated dental cream tubes, mechanically operated dental cream dispensers or flexible sachets, that syneresis becomes a problem and liquids separate from solids, rendering the dental cream undesirable.
In earlier commonly assigned patent disclosures additives to prevent dental cream syneresis upon contact with a polyolefin surface have been disclosed for dental creams containing an alkaline earth metal phosphate or alpha-alumina trihydrate polishing agent. These disclosures are:
U.S. Pat. No. 4,702,905, granted Oct. 27, 1989, wherein the anti-syneresis additive for an alkaline earth phosphate dental cream is a polyethylene glycol;
U.S. Pat. No. 4,716,034, granted Dec. 29, 1989, wherein the anti-syneresis additive for an alpha-alumina trihydrate dental cream is a polyethylene glycol;
U.S. Pat. No. 4,728,508, granted Mar. 1, 1988, wherein the anti-syneresis additive for a dental cream in which the polishing agent is mainly an alkaline earth metal phosphate is propylene glycol;
U.S. Pat. No. 4,770,324, granted Sept. 13, 1988, as a continuation-in-part of, now abandoned, U.S. Ser. No. 808,756, filed Dec. 13, 1985, wherein the anti-syneresis additive for a dental cream in which the polishing agent is mainly an alkaline earth metal phosphate is an alkyl parahydroxybenzoate ester;
U.S. Pat. No. 4,716,836, granted Dec. 29, 187, wherein the anti-syneresis additive for an alpha-alumina trihydrate dental cream is a vegetable oil;
U.S. Pat. No. 4,705,680, granted Nov. 10, 1987, wherein the anti-syneresis additive for an alkaline earth metal phosphate dental cream is a vegetable oil; and
U.S. Ser. No. 214,786, filed July 5, 1988, now abandoned, as a continuation of, U.S. Ser. No. 835,014, filed Feb. 28, 1986, wherein the anti-syneresis additive for a dental cream in which the polishing agent is mainly alpha-alumina trihydrate is benzoic acid.
In each of the foregoing patent disclosures condensates of ethylene oxide with propylene glycol, that is "Pluronic" materials, are generally disclosed as a type of surface-active material which may be present in the several dental creams containing the described particular anti-syneresis additives.
Japanese Public Disclosure No. 75410/85 to Ebine et al (Lion Corporation) describes a dentifrice in which glycerine is the sole humectant or mixed with another humectant, such as sorbitol, but which glycerine is, in any event, present in amount greater than 20% by weight of the dentifrice, since lesser amounts would result in undesirable evaporation of water when the dentifrice is packed in a container having a plastic container body, at least the barrel portion of which has a water permeability of at least 5g/m.sup.2.day.50u. The high glycerine dentifrice is formulated to avoid evaporation and weight loss in this particular type of container. The disclosure includes a general indication that polymer of ethylene oxide and propylene oxide may be employed as surface-active agent.
U.S. Pat. No. 4,556,553 to Suganuma et al (Lion Corporation) discloses dentifrices containing and aluminum oxide abrasive in a container having an oxygen permeability of at least 3cc/m.sup.2.day.atm wherein antiseptic properties are improved by the presence of polyhydric alcohol, including mixture of sorbitol and glycerine. There is a general disclosure that condensates of ethylene oxide with propylene oxide may be used as a surface-active agent in the aluminum oxide dentifrices. Some dentifrice samples are described for comparative purposes which contain dicalcium phosphate with sodium lauryl sulfate as the sole surface active agent.
Japanese Public Disclosure 1321/80 published on Japanese Patent Application 86226/78 to Naganuma et al (Lion Dentifrice Company) discloses that liquid-solid separation in toothpaste containing an anionic surfactant and a polyoxyethylene block copolymer type surfactant (that is, a "Pluronic" surfactant) can be overcome by employing a binder or gelling agent of at least one of hydroxyethyl cellulose and/or xanthan gum rather than carrageenan, gum tragacanth, sodium carboxymethyl cellulose, poly(sodium acrylate) or guar gum. The toothpastes described contain a humectant such as glycerin, sorbitol, propylene glycol or polyethylene glycol. The only mixtures of humectants described in specific formulations including those which evince separation when a gelling agent other than hydroxyethyl cellulose or xanthan is employed, contain glycerine and propylene glycol.
U.S. Pat. No. 4,353,890 to Scott (Colgate-Palmolive Company) discloses toothpastes containing carrageenan gelling agent which is stabilized by microwave radiation to maintain viscosity. A dicalcium phosphate toothpaste containing such stabilized carrageenan with a mixed humectant of 4.5% by weight of glycerol and 17.5% by weight of sorbitol is exemplified and indicated to be subjected to storage tests, including when packaged in containers having body portions of polyethylene. The detergent or surface-active agent employed in the exemplified toothpaste is sodium lauryl sulfate. The patent includes a general disclosure "Pluronics .sup.(R) " as detergents.
It is an advantage of this invention that phase separation of a dental cream packaged in contact with a polyolefin material which would undergo phase separation but for the presence of an additive which overcomes syneresis, is substantially prevented. Other advantages will be apparent from consideration of the following disclosure.